1. Technical Field of the Invention
The present invention relates to novel cosmetic/dermatological compositions comprising at least one extract of at least one plant from the genus Saxifraga, for the artificial tanning, browning and/or darkening of human skin, imparting thereto an artificial coloration closely resembling that of a natural tan, and to the use of such novel compositions for the cosmetic applications indicated above.
2. Description of the Prior Art
It is today increasingly important to have a healthy appearance, and tanned skin is always a sign of good health. However, a natural tan is not always desirable since it necessitates prolonged exposure to UV radiation, in particular to UV-A radiation which is liable to induce an adverse change in the skin, in particular in the case of sensitive skin or of skin which is continually exposed to solar radiation. It is thus desirable to provide an alternative to a natural tan, which is compatible with the requirements of such skin types.
Most of the cosmetic products intended for artificially tanning the skin are based on carbonyl compounds which, by interacting with the amino acids in the skin, permit the formation of colored species.
Thus, it is known to this art that dihydroxyacetone, or DHA, is a particularly advantageous substrate which is commonly employed in cosmetics as an artificial tanning agent for the skin; when applied to the skin, in particular to the face, it elicits a tanning or browning effect similar in appearance to that which may result from prolonged exposure to sunlight (natural tanning) or under a UV lamp.
Nonetheless, topical application of DHA may present certain drawbacks. Thus, DHA has an unfortunate tendency, which is more or less pronounced depending on the nature of the medium in which it is formulated, to degrade over time, this degradation generally being ultimately reflected by an undesirable yellowing of the compositions containing same. The effect of such a phenomenon is that the activity of DHA, and in particular its ability to color the skin, may be reduced at the point in time of application of these compositions onto the skin. Hence, the intensity of the coloration imparted to the skin may appear as still insufficient.
Another drawback of DHA is the slow speed at which the coloration develops: specifically, several hours are required (in general 3 to 5 hours) in order for the coloration to be revealed. Furthermore, the coloration produced on the skin by DHA is often considered as being too yellow by users.
There is thus an increasing demand for self-tanning products which act rapidly and provide a coloration which is closer to that of a natural tan.
With a view towards satisfying this need, it has been proposed to combine DHA with various products: thus, WO-95/15742 describes the combination of DHA with amino acids. However, the use of such combinations is highly impractical since it requires either a two-stage application or complex separate packagings. FR-2,726,761 describes the combination of DHA with lawsone and/or juglone: in this instance also, such combination is unsatisfactory, this time on account of the risks of sensitization provided thereby.
Thus, serious need continues to exist for novel products and novel compositions which can artificially impart to the skin a coloration closely approximating that of a natural tan in a simple, effective, rapid and risk-free manner.
It has now unexpectedly and surprisingly been determined that certain specific compounds impart to the skin a long-lasting artificial coloration closely resembling that of a natural tan, and this immediately after topically applying such compounds onto the skin.
Briefly, the present invention features novel cosmetic/dermatological compositions well suited for artificially tanning the skin, comprising, formulated into a physiologically acceptable support (vehicle, diluent or carrier), an effective self-tanning amount of at least one extract of at least one plant from the genus Saxifraga.
The present invention thus also features the use of at least one extract as described above in, or for the production of, compositions suited for artificially coloring the skin.
This invention also features a cosmetic regime/regimen for the skin to impart coloration thereto, comprising topically applying onto the skin an effective amount of an extract or of a cosmetic composition as described above.
The compositions and the applications thereof in accordance with the invention make it possible to obtain an artificial coloration close to that of a natural tan within an exceptionally short time period. Thus, an immediate coloration is obtained, which permits a visualization of the application and consequently better homogeneity in the spreading of the composition on the skin and thus the coloration resulting therefrom. Furthermore, the artificial coloration provided on the skin according to the invention is extremely close to that of a natural tan and also very resistant to water and to the environment/weather (it can persist on the skin for several days).
More particularly according to the present invention, the extracts employed are extracts of at least one plant from the genus Saxifraga, as described by G. Bonnier in La Grande Flore from Gaston Bonnier Editions Belin, Nov. 1990, Institut National de la Recherche Agronomique and Delachaux and Nestlxc3xa9 S. A. The invention thus relates to plants of the genus Saxifraga as described by G. Bonnier.
The plants of the genus Saxifraga are known on the one hand as ornamental plants, but also for phytotherapy applications because of their aperitive, astringent, cholagogic and/or diuretic properties.
However, their use as skin-coloring agents as described above was hitherto unknown.
The plants of the genus Saxifraga belong to the family of Saxifragacea and the genus comprises about 630 species, among which are, for example and without limitation, Saxifraga cuneifolia, Saxifraga glaucescens, Saxifraga rotundifolia, Saxifraga granulata, Saxifraga bulbifera, Saxifraga umbrosa and Saxifraga tridactylites. 
The extract of at least one plant from the genus Saxifraga according to the invention is advantageously an extract of a plant from a species selected from among Saxifraga cuneifolia, Saxifraga glaucescens, Saxifraga rotundifolia, Saxifraga granulata, Saxifraga bulbifera, Saxifraga umbrosa and Saxifraga tridactylites. 
In a preferred embodiment of the invention, the extract of at least one plant from the genus Saxifraga is an extract of a plant from a species selected from among Saxifraga glaucescens, Saxifraga rotundifolia and Saxifraga granulata. 
The extract of at least one plant from the genus Saxifraga according to the invention can be recovered from plant material derived from the whole plant or from a plant part such as the leaves, stems, flowers, petals or roots, or alternatively from undifferentiated cells thereof.
By the expression xe2x80x9cundifferentiated plant cellsxe2x80x9d is intended any plant cell which exhibits none of the characteristics of a specific specialization and which is capable of living by itself and independently of other cells.
According to the invention, the whole or entire plant is preferably employed, particularly the stem and/or the leaves and most preferably the leaves.
The extract of at least one plant from the genus Saxifraga can be any extract prepared from any plant material derived from at least one plant from the genus Saxifraga cultivated in vivo or obtained from in vitro culturing.
By the expression xe2x80x9cin vivo culturingxe2x80x9d is intended any culturing of conventional type, i.e., in soil in the open air or in a greenhouse, or alternatively without soil.
By the expression xe2x80x9cin vitro culturingxe2x80x9d is intended the set of techniques known to this art which makes it possible to artificially obtain a plant or a part of a plant. The pressure of selection imposed by the physicochemical conditions during the growth of the plant cells in vitro produces a standardized plant material which is available throughout the year, unlike plants cultivated in vivo.
According to the invention, a plant of the genus Saxifraga obtained via in vitro culturing is preferably employed.
Any extraction technique known to this art can be used to separate the extract according to the invention.
Particularly exemplary are alcoholic extracts, in particular ethanolic extracts, or aqueous/alcoholic extracts.
The extract is preferably an aqueous extract.
An extract prepared via the technique described in FR-95/02379, assigned to the assignee hereof, can also be used.
Thus, in a first step, the plant material is ground in an aqueous solution under cold conditions, and, in a second step, the particles in suspension are removed from the aqueous solution obtained in the first step. This aqueous solution corresponds to the extract.
The aqueous solution obtained from the second step is optionally sterilized in a third step.
This extract can then be lyophilized.
The first step can be advantageously replaced with an operation of simple freezing of the plant tissues (for example at xe2x88x9220xc2x0 C. or at xe2x88x92180xc2x0 C. in liquid nitrogen), followed by aqueous extraction repeating the second and third steps described above.
The cold-temperature treatment allows the enzymative activities to be frozen, and the sterilizing filtration avoids the degradation of the active agents by environmental microorganisms. Finally, the water vehicle is compatible with the ex vivo receptors and facilitates cosmetic or pharmaceutical formulations.
It is known that plant extracts contain oxidases that are responsible, inter alia, for the oxidation of said extracts. In point of fact, such oxidation imparts to the extracts a dark brown coloration and an acrid odor, thus making them unsuitable for formulation into cosmetics. Similarly, a lactase whose molecular weight is greater than 100,000 daltons is known, in particular.
Thus, the extract obtained can be advantageously fractionated by any known fractionation technique for removing oxidases, and in particular polyphenol oxidase. For example, the extract of the invention can be filtered through a dialysis membrane in order to remove the molecules whose molecular weight is greater than 100,000 daltons. It is also possible to subject the extract to a fractionation by selective precipitations.
Other methods make it possible to protect against oxidation phenomena. In particular, the extract can also be stabilized. Any known stabilization method can be used according to the invention. For example, the extract of the invention can be stabilized by bubbling nitrogen therethrough in order to remove the dissolved oxygen, or alternatively by adding cysteine and/or sulfur derivatives thereto to a final concentration ranging from 0.5 g/l to 10 g/l and preferably from 1 g/l to 2.5 g/l.
It will of course be appreciated that the extract according to the invention can be fractionated and stabilized.
The extract can itself constitute the active principle of the compositions of the invention.
One embodiment of a preparation of an extract which can be employed according to the invention is given in the examples which follow.
The extract of at least one plant from the genus Saxifraga is preferably present in the compositions according to the invention in proportions that are sufficient to impart to the skin, after application, a coloration similar to the coloration obtained after natural tanning. It is thus generally present in proportions of ranging from 0.05% to 20% by weight relative to the total weight of the composition, and preferably from 0.5% to 10% by weight relative to the total weight of the composition.
It will also be appreciated that the compositions of the present invention can contain one or more other skin-coloring agents such as, for example, mono- or polycarbonyl compounds such as isatin, alloxan, ninhydrin, glyceraldehyde, mesotartaric aldehyde, or pyrazoline-4,5-dione compounds, and these skin-coloring agents may be combined with direct dyes or indole derivatives.
In one preferred embodiment of the invention, the compositions also comprise dihydroxyacetone (DHA).
Thus, the present invention also features compositions which comprise, formulated into a physiologically acceptable support, an extract of at least one plant from the genus Saxifraga as described above and at least one other skin-coloring agent. According to the invention, such other skin-coloring agent is preferably selected from among mono- or polycarbonyl compounds such as isatin, alloxan, ninhydrin, glyceraldehyde, mesotartaric aldehyde, pyrazoline-4,5-dione compounds and dihydroxyacetone.
The other skin-coloring agent is very preferably dihydroxyacetone (DHA).
Specifically, dihydroxyacetone and the extracts of at least one plant from the genus Saxifraga described above exhibit excellent chemical compatibility in compositions comprised thereof, as well as very good complementarity of the colorations they impart to the skin. This makes it possible, by combining these in suitable proportions, to achieve an artificial skin coloration that is remarkably close to the coloration imparted by natural tanning.
The other skin-coloring agent is advantageously present in the compositions according to the invention in proportions which allow the combination of the two skin-coloring agents to impart to the skin, after application, a coloration which is as close as possible to that provided by natural tanning. The skin-coloring agent is thus generally present in an amount by weight ranging from 0.5% to 10% relative to the total weight of the composition, and preferably from 1% to 7% by weight relative to the total weight of the composition.
The dihydroxyacetone can also be applied to the skin in the form of an independent composition, separately of the composition comprising the extract of at least one plant from the genus Saxifraga, for example before or after applying the latter composition.
In another preferred embodiment of the cosmetic regime/regimen according to the invention, a composition comprising dihydroxyacetone is topically applied in a first stage, and the composition comprising the extract of at least one plant from the genus Saxifraga is then topically applied in a second stage, in order, at the user""s discretion, to modify the shade of the coloration provided by dihydroxyacetone alone, which is occasionally considered as being slightly too yellow.
The compositions according to the invention can also contain one or more hydrophilic or lipophilic sunscreens that are active in the UVA and/or UVB range, or, alternatively, coated or uncoated metal oxide pigments.
The compositions according to the invention can be cosmetic or dermatological compositions. Consistent herewith, the compositions are preferably cosmetic formulations.
The compositions of this invention can also comprise conventional adjuvants and additives selected, in particular, from among fatty substances, organic solvents, ionic or nonionic thickeners, softeners, antioxidants, free-radical scavengers, opacifiers, stabilizers, emollients, silicones, xcex1-hydroxy acids, antifoaming agents, moisturizers, vitamins, fragrances, preservatives, surfactants, fillers, sequestering agents, polymers, propellants, acidifying or basifying agents, dyes, colorants, or any other ingredient conventional in this field, in particular for the formulation of antisun/sunscreen compositions as emulsions.
The fatty substances are advantageously oils or waxes or mixtures thereof. By the term xe2x80x9coilxe2x80x9d is intended a compound which is liquid at room temperature. By the term xe2x80x9cwaxxe2x80x9d is intended a compound which is solid or substantially solid at room temperature, and whose melting point is generally greater than 35xc2x0 C.
Exemplary oils are mineral oils (petroleum jelly); plant oils (sweet almond oil, macadamia oil, blackcurrant seed oil or jojoba oil); synthetic oils such as perhydrosqualene, fatty alcohols, fatty acids or fatty esters (such as the C12-C15 alkyl benzoate marketed under the trademark xe2x80x9cFinsolv TNxe2x80x9d by Finetex, octyl palmitate, isopropyl lanolate, triglycerides including those of capric/caprylic acids), oxyethylenated or oxypropylenated fatty esters and fatty ethers; silicone oils (cyclomethicone, polydimethylsiloxanes or PDMSs) or fluoro oils, and polyalkylenes.
Exemplary waxy compounds are paraffin, carnauba wax, beeswax and hydrogenated castor oil.
Exemplary organic solvents are the lower alcohols and polyols.
And exemplary thickeners include, in particular, crosslinked polyacrylic acids and modified or unmodified guar gums and celluloses, such as hydroxypropyl guar gum, methylhydroxyethylcellulose and hydroxypropylmethylcellulose.
One skilled in this art will of course take care to select the optional additional compound(s) indicated above and/or the amounts thereof such that the advantageous properties intrinsically associated with the use of at least one extract of at least one plant from the genus Saxifraga in accordance with the invention are not, or are not substantially, adversely affected by the addition(s) envisaged.
The compositions according to the invention can be formulated according to the techniques that are well known to those skilled in the art, in particular those suitable for the formulation of emulsions of oil-in-water (O/W) or water-in-oil (W/O) type.
Such a composition can be, in particular, in the form of a simple or complex emulsion (O/W, W/O, O/W/O or W/O/W emulsion) such as a cream or a milk, or in the form of a gel or a cream/gel, in the form of a lotion, an ointment, a powder or a solid tube or stick, and can optionally be packaged as an aerosol and can be in the form of a mousse or a spray.
The compositions according to the invention are preferably oil-in-water emulsions.
When the composition is an emulsion, the aqueous phase of this composition can comprise a nonionic vesicular dispersion formulated according to known processes (Bangham, Standish and Watkins, J. Mol. Biol., 13, 238 (1965), FR-2,315,991 and FR-2,416,008).